Art of manufacturing hollow core concrete planks



y 7, 1968 R. H. NAGY 3,382,304

ART OF MANUFACTURING HOLLOW CURE CONCRETE PLANKS Filed Jan. 14, 1966 3 Sheets-Sheet 1 INVENTOR ROBERT H. NAGY ATTORNEYS May 7, R. H. NAGY ART OF MANUFACTURING HOLLOW CORE CONCRETE PLANKS Filed Jan. 14, 1966 3 Sheets-Sheet 2 Q INVENTOR W44 BY M9 ATTORNEYS R. H. NAGY ART OF MANUFACTURING HOLLOW CORE CONCRETE PLANKS Filed Jan. 14, 1966 3 Sheets-Sheet 3 VENTOR OBERT H. NAGY TTORNEYS United States Patent 3,382,304 ART OF MANUFACTURING HOLLOW CORE CONCRETE PLANKS Robert H. Nagy, 2421 N. 111th St., Milwaukee, Wis. 53226 Filed Jan. 14, 1966, Ser. No. 520,581 8 Claims. (Cl. 264-70) This invention relates to improvements in the art of manufacturing hollow core concrete planks.

This invention relates in general to the manufacture of hollow core concrete planks by use of apparatus of the general type disclosed in Schafer Patent No. 1,920,716. The machine of this patent has material hoppers and tamping elements, and is mounted for travel lengthwise of the planks being formed. The machine discharges layers of concrete from the hoppers, one layer over another, and also carries a plurality of core elements which are pulled longitudinally through the middle layer of concrete. The tamping elements operate above the core elements and are adapted to tamp the concrete over the core elements.

With methods as heretofore employed the forcing of the concrete down and between the narrow portions of the concrete webs between the cores has presented a problem. Heretofore there has been a tendency for the concrete which is being tamped to bridge between the upper portions of two core elements without getting down into the narrow region therebelow between cores. This created weak areas in the plank at these narrow portions of the webs, and there was the possibility of the plank shearing at one of these weak areas after the finished plank was placed in use.

It is a general object of the present invention to provide an improved method of manufacturing hollow core concrete planks wherein novel steps are employed to provide for proper movement and compaction of the concrete into the narrow portions of the webs between cores throughout the depth of said web portions to thereby eliminate the possibility of weak areas.

A further object of the invention is to provide improved apparatus for effecting commercial exploitation of the improved method.

With the above and other objects in view, the invention consists of the improvements in the art of manufacturing hollow core concrete planks and all of its parts, combinations and steps, as set forth in the claims, and all equivalents thereof.

In the accompanying drawings, illustrating one complete embodiment of the preferred form of the invention, in which the same reference numerals designate the same parts in all of the views:

FIG. 1 is a partially diagrammatic side elevational view of the improved machine;

FIG. 2 is a fragmentary perspective view of the first middle tamper;

FIG. 3 is a fragmentary perspective view of the second middle tamper;

FIG. 4 is a perspective view of the tamping screed;

FIG. 5 is a transverse section taken on the line 55 of FIG 4;

FIG. 6 is a transverse sectional view through a portion of a nearly finished concrete plank showing in diagrammatic form the relationship of the lugs of the progressive tamping members therewith.

Referring more particularly to the drawings, first to FIG. 1, the numeral 20 designates a floor or bed on which the concrete plank is to be laid. The numeral 21 designates generally the apparatus for manufacturing the hollow core concrete planks. This apparatus includes a first hopper 22 for the mix of concrete which is to form the bottom layer of the concrete plank, said hopper having a bottom opening 23. There is also a middle hopper 24 for 3,382,304 Patented May 7, 1968 a mix of concrete which is to form the middle layer, said hopper 24 having a bottom opening 25. In addition there is a hopper 26 for the concrete which is to form the top layer, which hopper is adapted to discharge through a chute 27 into another hopper 28 leading to a discharge section 29 having a bottom opening 30.

The present invention is concerned with the apparatus and method for tamping and compacting the middle layer over and between the hollow elongated tubes 31 which 1 form the longitudinal core openings 32 in the final product (see FIG. 6). These core-forming tubes 30 have tapered forward ends 33 for plowing through the freshly poured concrete, the elements 31 being suitably suspended for short longitudinal reciprocating strokes from a support 34, the later being suitably suspended from the frame of the machine.

As is well known in apparatus of this type, and as fully described in the Schafer Patent No. 1,920,716, the apparatus 21 is suitably mounted for movement in the direction indicated by the arrow in FIG. 1 so that multiple layers of a plank may be progressively poured as the apparatus is moved, the core elements 31 being so located that the mix for the middle layer is discharged over the tapered noses 33 so that the tubes 31 may be pulled therethrough. There is provision for longitudinally reciprocating the core elements 31 as they are moved through the concrete of the middle layer as heretofore mentioned. As is customary with apparatus of this type, and as also fully described in Schafer Patent No. 1,920,716 and in Young Patent No. 2,962,785, there are pretensioned wires 35 in the bottom layer (see FIG. 6), and there are preliminary tampers 36 and 37 which are suitably supported for tamping movement and which preferably have a scalloped or grooved lower surface, as fully described in Young Patent No. 2,962,785, for forming ridges 38 over the wires (see FIG. 6), which ridges extend in the same direction as the wires. The tamping members 36 and 37 also preferably have spaced surfaces between grooves located to compact the concrete as at 39 between wires, said compacting surfaces also forming valleys for receiving the lower portions of the core elements 31. Suitably supported for tamping motion at the rear of the discharge opening 25 of the hopper for the middle mix is a tamper 40 which is of conventional construction and which also serves as a flow control for the middle hopper 24.

The present invention is concerned m'th the tampers which follow the tamper 40, and these novel tampers are especially designed to properly direct and compact the concrete of the middle layer between the core elements 31 to avoid weak regions at the narrow portions 41 of the ultimate concrete webs. Heretofore there was a tendency, when conventional tampers were used, to cause the concrete to bridge, as indicated by the dot and dash lines 42 in FIG. 6, with said bridges forming bottlenecks to prevent the concrete from moving down into the narrow regions 41 just below the bridges. It is the principal object of the present invention to provide for good filling and compaction in the regions 41, and to prevent the type of bridging indicated at 42.

There are two middle tampers 43 and 44 suitably mounted for tamping movement on the machine 21. The tamper 43 is constructed as shown in FIG. 2 and has a leading or first stage tamping surface formed with spaced lugs 45 having relatively flat bottoms 46 and having angled sides 47. The sides 47 are obliquely angled, preferably at approximately 60 from the horizontal (see also FIG. 6). Between each pair of lugs is an inverted concrete receiving pocket. Behind the first stage lugs 45 are second stage lugs 49. Each lug 49 has a flat bottom 50 and angled sides 51. The sides 51 are preferably at an angle of 45, as is indicated in FIG. 6. It is essential that the angles in the second stage be substantially flatter than the angles in the first stage. It is to be noted that the lugs 50 are mounted on a spacer bar 52, the bottom of which forms surfaces 53 between the lugs 43, which surfaces are spaced substantially below the corresponding surfaces 48 of the first stage so that the inverted pockets of the second stage have lower roofs and are generally flatter. In addition, it is apparent from FIGS. 2 and 6 that the bottoms 50 of the lugs 49 project below the bottoms 46 of the lugs 45.

The tamper 44 also has its tamping surface formed in first and second stages, as shown in FIGS. 3 and 6. Here the first stage has spaced lugs 54 having bottoms 55 and inclined sides 56. The sides 56 are preferably at approximately the same angle as the sides of the second stage lugs 45 of the tamper of FIG. 2; that is, at about a 45 angle. Between the lugs 54 are flat areas 57. The second stage of the tamping element 44 includes lugs 58 having bottoms 59 with inclined sides 60. The sides 60 are a at substantially flatter angle than the sides 56, and are preferably at an angle of about 30, as is shown in FIG. 6. The lugs 58 are mounted on a spacer bar 61, the lower surfaces of which form flat areas 62 between the lugs 58 which are spaced well below the corresponding areas 57 of the first stage. Thus the inverted pockets between lugs are progressively shallower. In addition, the bottoms 59 project below the bottoms 55, as is clear from FIG. 6. While the second stage lugs of FIGS. 2 and 3 are shown as supported on spacer bars 52 and 61, respectively, it is obvious that the elements of FIGS. 2 and 3 may be cast integrally to form the shapes shown in FIGS. 2 or 3.

Rearwardly of the tamper 44 is a tamping screed 63 suitably supported for vibrating or tamping motion. While a conventional flat tamper may be used for 6" or 8" planks, it is desirable, but not essential, for 10" or thicker planks to have a special screed as hereinafter described. The screed 63 is illustrated in FIGS. 4 and 5. Its bottom surface, at the leading edge, presents depending lugs 64 having inclined sides 65 which start at approximately the same angle as the angle of the sides 30 of the lugs 58, which angle is preferably 30. The lugs of the screed, however, gradually flatten toward the trailing edge portion 66 which is a flat plane, and said lugs merge into said plane and disappear.

The purpose of the gradually decreasing angles of the sides of the tamping lugs, and of having the flat roof areas 53 between lugs (FIG. 2) lower than the areas 48, and the roof areas 62 between lugs lower than the areas 57 (FIG. 3), is to form inverted pockets between lugs which are progressively flatter and shallower to progressively act on the concrete in a manner to eliminate possible bridging of the concrete in the areas 42, FIG. 6, as heretofore mentioned.

Referring to the vector arrows in FIG. 6, the resultant forces indicated by the arrows F F F F and F and which are at an angle, progressively change toward the vertical. In addition, the tops 48, 53, 57 and 52 of the recesses between lugs are progressively lower. Thus inverted pockets which are progressively flatter and shallower are formed. When the flat lug bottoms 46 of the first stage of FIG. 2 come down they compact the concrete over the tops of the core elements 31. Inasmuch as these areas 46., 50, 55 and 59 are progressively lower as the machine advances they progressively compact to a denser and denser condition over the tops of the cores. However not much concrete is needed over the tops of the cores. Therefore, these flat lug bottoms 46, 50, 55 and 59 of the lugs squeeze much of the concrete which was originally above the core elements 31 laterally into the inverted pockets between lugs so that they can be acted upon by the inclined sides and tops of these pockets. Inasmuch as these inclined sides progressively approach a flat plane, and inasmuch as the tops of the recesses are progressively lower, the result is to progressively squeeze and push the surplus concrete down into and toward the weak portions 41 of the webs, where a greater quantity of concrete is needed. By thus progressively packing this greater mass of concrete downwardly and toward the weak portions 41 of the webs, any bridge which might have a tendency to form (as at 42, FIG. 6) is quickly broken to allow the concrete to get down below to the weak areas 41 to form a dense compaction throughout the narrow portions of the webs. As the tamping surfaces gradually approach a flat plane the resultant force is more and more toward the vertical to give a final compaction over the webs. In cases where a screed of the type shown in FIG. 4 is used this final compaction is delivered by the flat rear portion 66 of the screed. In thinner planks where a conventional tamper may be substituted for the screed of FIG. 4, the flat tamper does the same job of final compaction over the web portions.

In use of the invention the tamping members are, of course, pulled along with the machine as they are engaged in tamping action so that the middle layer of concrete, just after being deposited, is first engaged by the first stage of tamping member 43, then by the second stage of tamping member 43, next by the first stage of tamping member 44, then by the second stage of tamping member 44, and thereafter by the tamping screed 63. The result is a very effective tamping of concrete into the regions 41 between cores to eliminate voids below the regions 42 which would otherwise be caused by concrete bridging in the manner suggested at 42, FIG. 6. The invention is particularly useful when forming relatively thick planks such as 10" planks, where the problem is very acute because it is harder to get compactness in the regions 41 of a thick plank. The process, however, will improve the characteristics of planks of less thickness such as 8 and 6" planks. The plank shown in FIG. 6 is adapted to be completed by a finishing layer (not shown) over the middle layer, which finishing layer is deposited by the hopper spout 30 and smoothed by the reciprocating trowels 68 and 67.

Various changes and modifications may be made without departing from the spirit of the invention, and all of such changes are contemplated as may come within the scope of the claims.

What I claim is:

1. In a movable machine for manufacturing hollow core concrete planks having longitudinally-extending transversely-spaced core elements supported therefrom and having a hopper positioned to discharge concrete on the forward portions of said core elements, tamping means supported for tamping movement over the core elements and including a plurality of transverse tamping surfaces positioned one behind another in the direction of movement of the machine, each transverse tamping surface having transversely-spaced lugs with bottom compacting surfaces separated by inverted pockets having angled sides, the lugs being so arranged that their bottom compacting surfaces are over the tops of the core elements to compact the concrete thereover and squeeze it laterally over the region between core elements to be acted upon by said pockets, said pockets of a trailing transverse tamping surface being shallower and the angular sides being flatter than the pockets of a forwardlypositioned transverse tamping surface to thereby progressively direct concrete into and compact it below those narrow regions between core elements where bridging might otherwise occur.

2. A machine as claimed in claim 1 in which the tamping means includes two relatively movable tamping members one behind another, each tamping member having a plurality of said transverse tamping surfaces, with the inverted pockets of one tamping surface being shallower and flatter than the inverted pockets of a forwardlypositioned tamping surface of the same tamping member.

3. A machine as claimed in claim 2 in which at least one of said transverse tamping surfaces of one tamping member has its inverted pockets shallower and flatter than the pockets of a tamping surface of a forwardlypositioned tamping member.

4. A machine as claimed in claim 2 in which there is a movably-supported tamping screed which trails the two relatively-movable tamping members and which has a transverse tamping surface having transversely-spaced lugs with intervening inverted pockets, wherein said lugs and pockets are progressively flatter in a trailing direction to merge into a substantially flat, horizontal, transverse screed surface.

5. A machine as claimed in claim 1 in which the lugs of a trailing tamping surface normally project below the lugs of a forwardly-positioned transverse tamping surface.

6. A machine as claimed in claim 1 in which the angular sides of the inverted pockets of a tamping surface are at approximately 45 from horizontal and the angular sides of the inverted pockets of a tamping surface which is positioned forwardly therefrom are at approximately 60 from horizontal.

7. A machine as claimed in claim 2 in which the angled sides of the inverted pockets of a tamping surface of one movable tamping member are approximately 45 from horizontal, with the angular sides of the inverted pockets of a forwardly-positioned tamping surface of the same tamping member at approximately 60 from horizontal and in which the corresponding angles on a relatively movable tamping member therebehind are approximately by downward tamping forces and also by converging angular forces which are directed angularly downwardly from opposite directions toward the narrow regions between core elements, causing said downward forces to progressively compact in a downward direction, and causing said angular forces to progressively change in direction so as to approach closer to vertical, whereby to gradually direct material into said narrow regions and compact it therein while preventing bridging of the concrete over said narrow regions.

References Cited UNITED STATES PATENTS 1,063,039 5/1913 Kammer 25-41 1,521,292 12/1924 Harrison 2541 1,913,455 6/1933 Preston 2541 1,920,716 8/1933 Schafer 25-41 WILLIAM J. STEPHENSON, Primary Examiner. 

1. IN A MOVABLE MACHINE FOR MANUFACTURING HOLLOW CORE CONCRETE PLANKS HAVING LONGITUDINALLY-EXTENDING TRANSVERSELY-SPACED CORE ELEMENTS SUPPORTED THEREFROM AND HAVING A HOPPER POSITIONED TO DISCHARGE CONCRETE ON THE FORWARD PORTIONS OF SAID CORE ELEMENTS, TAMPING MEANS SUPPORTED FOR TAMPING MOVEMENT OVER THE CORE ELEMENTS AND INCLUDING A PLURALITY OF TRANSVERSE TAMPING SURFACES POSITIONED ONE BEHIND ANOTHER IN THE DIRECTION OF MOVEMENT OF THE MACHINE, EACH TRANSVERSE TAMPING SURFACE HAVING TRANSVERSELY-SPACED LUGS WITH BOTTOM COMPACTING SURFACES SEPARATED BY INVERTED POCKETS HAVING ANGLED SIDES, THE LUGS BEING SO ARRANGED THAT THEIR BOTTOM COMPACTING SURFACES ARE OVER THE TOPS OF THE CORE ELEMENTS TO COMPACT THE CONCRETE THEREOVER AND SQUEEZE IT LATERALLY OVER THE REGION BETWEEN CORE ELEMENTS TO BE ACTED UPON BY SAID POCKETS, SAID POCKETS OF A TRAILING TRANSVERSE TAMPING SURFACE BEING SHALLOWER AND THE ANGULAR SIDES BEING FLATTER THAN THE POCKETS OF A FORWARDLYPOSITIONED TRANSVERSE TAMPING SURFACE TO THEREBY PROGRESSIVELY DIRECT CONCRETE INTO AND COMPACT IT BELOW THOSE NARROW REGIONS BETWEEN CORE ELEMENTS WHERE BRIDGING MIGHT OTHERWISE OCCUR.
 8. IN A METHOD OF MANUFACTURING HOLLOW CORE CONCRETE PLANKS WHEREIN A CONCRETE LAYER IS LAID OVER TRANSVERSELYSPACED, LONGITUDINALLY-EXTENDING CORE ELEMENTS, THE STEPS OF TAMPING THE CONCRETE LAYER IN A MANNER TO COMPACT THE CONCRETE OVER THE TOPS OF THE CORE ELEMENTS AND SIMULTANEOUSLY SQUEEZE IT LATERALLY IN BOTH DIRECTIONS OVER THE SPACES BETWEEN CORE ELEMENTS TO CRATE SUPLUSES IN THESE REGIONS, ACTING ON THE SURPLUS CONCRETE OVER SAID SPACES BY DOWNWARD TAMPING FORCES AND ALSO BY CONVERGING ANGULAR FORCES WHICH ARE DIRECTED ANGULARLY DOWNWARDLY FROM OPPOSITE DIRECTIONS TOWARD THE NARROW REGIONS BETWEEN CORE ELEMENTS, CAUSING SAID DOWNWARD FORCES TO PROGRESSIVELY COMPACT IN A DOWNWARD DIRECTION, AND CAUSING SAID ANGULAR FORCES TO PROGESSIVELY CHANGE IN DIRECTION SO AS TO APPROACH CLOSER TO VERTICAL, WHEREBY TO GRADUALLY DIRECT MATERIAL INTO SAID NARROW REGIONS AND COMPACT IT THEREIN WHILE PREVENTING BRIDGING OF THE CONCRETE OVER SAID NARROW REGIONS. 